Sinornithosaurus

Sinornithosaurus was a small, basal dromaeosaurid dinosaur discovered in the Jehol Biota of Liaoning, China. Dating to the Early Cretaceous, it was among the earliest dromaeosaurs found with exceptionally preserved feather impressions, providing crucial evidence bridging non-avian dinosaurs and early avians. Roughly the size of a pheasant or domestic cat, it possessed long legs, grasping forelimbs, and a slender, flexible body. The skull featured large teeth, which led one research team to speculate that grooves in the dentition accommodated venom delivery, though this interpretation has since been largely dismissed by fellow palaeontologists as normal crushed theropod anatomy. Sinornithosaurus was an active carnivore hunting in forest undergrowth and low branches, likely pursuing insects, small lizards, and juvenile mammals using sharp sight and agile bipedal movements.

A hypothesis that it possessed a venomous bite was widely popularised, but subsequent studies showed the skull features are typical for dromaeosaurs.

Where and when

Sinornithosaurus lived in the Early Cretaceous, from 125 to 122 million years ago (Aptian age). Its remains come from China, in the Yixian Formation.

The numbers

Length 1.2 m (estimates run from 1.1 to 1.3 m). Mass about 3.2 kg. Hip height about 0.4 m. That is 0.7 human-lengths, or 0.11 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, hip height.

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